NEW YORK (AP) -- Be careful what you wish for, Jack Donaghy.

The corporate titan (Alec Baldwin) of NBC's "30 Rock" finds his natural dad in Thursday's episode, one week after an episode in which his mother inadvertently reveals that the man he thought was his father wasn't.

Things move quickly in sitcom land, don't they?

Not before a few fun side trips, though. Jenna Maroney (Jane Krakowski) coins a new catchphrase — "that's a deal-breaker, ladies" — and is reluctant to share credit with the woman who actually wrote it, Liz Lemon (Tina Fey). Is this art imitating reality here? Is there something Fey wants her props for from her days on "Saturday Night Live"?

Lemon horns in on a Maroney photo shoot and isn't savvy enough to recognize a photographer who wants to make her look stupid.

Liz also recognizes she has a problem guessing the ages of African-Americans. She's a little surprised when Tracy Jordan (Tracy Morgan) tells her that he's 39.

"Why would I lie about my age?" Jordan says. "I'm in the entertainment industry."

Back to dad. With the help of a private investigator (Steve Buscemi), Donaghy tracks down the man whose drunken one-night stand with his mother produced him.

He's Milton Green (Alan Alda). Alda is playing precisely the role that his looks and demeanor suggest, when you think about it. He's a professor at Bennington College and, as might be expected, loudly argues with Donaghy about politics. Seems the picture of Donaghy "with" Tom DeLay didn't turn him on.

"It's exactly what I was afraid of," Donaghy tells Lemon. "More family, more aggravation."

Anyway, Green acts warmly when Donaghy tells him the next day that they are father and son. They hug, Donaghy's eyes grow moist, but Green has a surprise for him.

"I need a kidney," he said.

Oops.

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NBC is owned by General Electric Co.

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On the Net:

http://www.nbc.com/30—Rock/